This invention relates generally to highway trailers of the type used to transport large equipment such as farm combines over highways and other roadways. More particularly, the invention is directed to a trailer that is specially constructed to convert to different configurations, including a double drop deck configuration and a step deck configuration.
Various trailer bed configurations have been used for transporting large farm combines and other heavy machinery from one place to another. The equipment that needs to be hauled has increased in both size and weight in recent years. Accordingly, trailers have had to be enlarged and strengthened in order to handle both the increased size and weight. The trailer design also must comply with height limitations so that the equipment that is carried is able to clear overpasses and overhead utility lines.
A trailer configuration that is commonly known as a double drop deck configuration has achieved considerable popularity. In this configuration, there is a gooseneck section in the front coupled to the highway tractor that pulls the trailer. A relatively long center section provides a main deck that is lower than the deck of the gooseneck section. A rear section mounted on wheels has a relatively short deck that is raised above the level of the center deck. Thus, in the double drop deck trailer, the center deck that carries heavy equipment is dropped below the level both of the gooseneck deck and the rear deck.
The double drop deck trailer has advantages in many applications. The center deck is relatively low, so tall equipment can be transported in compliance with maximum height limitations. However, the gooseneck and rear decks are not available for carrying the large equipment because they are at a higher level than the center deck. Consequently, only the length of the center deck can be used for the large equipment. If timber, pipe or other cargo that is longer than the center deck is to be carried, the double drop deck trailer is not suitable. This is a serious limitation as to the application of the double drop deck trailer.
Another popular configuration is known as a step deck configuration. A step deck trailer has the center and rear decks at the same elevation so that longer cargo can be carried using the combined length of both decks. However, the rear deck must be high enough to accommodate the underlying trailer wheels, and the center deck must be at the same elevation. The result is that the main bed area is necessarily higher than the center deck in a double drop deck trailer. Therefore, the step deck trailer cannot carry equipment as tall as a double drop deck trailer can carry. Also, the gooseneck deck is still not available in a step deck trailer because it is above the center deck level. Step deck trailers are useful primarily to haul long pipes, timbers and other long loads that do not have height problems.
Still another trailer configuration is a straight deck configuration in which all of the decks are at the same level to provide one long deck surface extending the entire length of the trailer. While this configuration has advantages in some applications, such as when extremely long cargo is carried, the bed must be relatively high so that it is able to clear the wheels. Thus, straight deck trailers are not suitable for hauling tall equipment and are mainly used only to handle extremely long loads.
Loading of cargo onto existing trailers can also present problems. In order to load cargo onto a double drop deck trailer from the back, ramps are needed first to load the cargo up onto the back deck and then down onto the main bed. The inconvenience involved in this process has led to front loading systems which accommodate disconnection of the gooseneck from the center section so that the cargo can be loaded directly onto the main bed from the front. However, the systems that have been used for connection and disconnection of the gooseneck section have been complicated, expensive and time consuming.
The present invention has, as its principal object, the provision of a single trailer that is adjustable between different bed configurations to obtain the advantages of different types of trailers in a single trailer construction.
More specifically, one object of the invention is to provide a trailer that is specially constructed such that it can be converted between a double drop deck configuration and a step deck configuration. This allows the height advantage of a double drop deck trailer to be used when needed and the length advantage of a step deck trailer to be used when needed. For example, if a tall farm combine or other tall machinery is to be transported, the double drop deck configuration can be used. Alternatively, in an application involving pipe or other cargo that is too long to be transported on a double drop deck trailer, the step deck configuration can be used.
Another important object of the invention is to provide a trailer of the character described that can also be converted to a single deck configuration, thus accommodating a situation where extremely long cargo must be transported.
It is a further object of the invention to provide a trailer of the character described that can be quickly, easily and safely converted between the different configurations and used safely and effectively in each different configuration.
A still further object of the invention is to provide a trailer having a special connection between the main bed and the gooseneck section to enable detachment of the gooseneck so that cargo can be directly loaded onto and unloaded from the main bed from the front.
In accordance with the invention, a front gooseneck trailer section, a center section and a rear section are all constructed using four horizontal beams. The gooseneck and rear sections have upright portions formed by spaced apart legs that are received in U-shaped guide brackets on the front and rear ends of the center section. Due to this construction, the legs are able to slide in the brackets to adjust the center section up and down to different trailer configurations, preferably including a double drop deck configuration, a step deck configuration, and a straight deck configuration.
The center section may be provided with hydraulic jacks at its forward and rearward ends to permit adjustment between the different configurations to be quickly and easily carried out. Hydraulic latching cylinders mounted on the center section have rods that may be extended into passages in the legs of the gooseneck and rear sections to lock the center section rigidly in place. As an additional safety and reliability measure, a manual locking system includes U-shaped bars that may be manually applied into openings in the different trailer sections in order to lock them together in cooperation with the locking cylinders.
Another aspect of the invention is a special connection between the gooseneck section and the main bed. Pegs which normally fit in passages to assist in connecting these two sections together can be separated by rocking action provided by strategically located cylinders. After the sections have been detached by withdrawal of the pegs from the passages, the front of the bed section can be lowered to the ground where it is easily accessible for the loading and unloading of cargo.